Rohde & Schwarz R&S FSP Series, Operating Manual

Page: 339 / 796

Operating Manual 1164.4556.12 - 06 4.267
R&S FSP Instrument Functions
LO/IF ports for external mixers - Option R&S FSP-B21
Frequency range
The frequency of the input signal can be expressed as a function of the LO fre-
quency and the selected harmonic of the 1st LO as follows:
f
in
= n * f
LO
+ f
IF
where:
Full-screen level
The maximum reference level to be set is 0 dBm. If an IF signal with a level of -20
dBm is applied to the LO OUT / IF IN or IF IN input of the R&S FSP, full screen level
will be attained.
When digital filters are used (IF bandwidths = 100 kHz) the overload limit is typically
approx. 3 dB above the set reference level. IF signals with higher levels cause the A/
D converter to be overloaded (display ‘IFOVL’).
If an analog IF filter is used, the overload limit is determined by the IF amplifier. In
this case, the 1 dB compression point is approximately 6 dB above the reference
level. Overload display ‘OVL’ appears at higher levels.
In addition to the dynamic range of the R&S FSP, the 1 dB compression point of the
mixer has to be taken into account. The levels of the input signals should lie well
below this value to avoid generation of harmonics of these signals in the mixer.
These are converted by the LO signals harmonics of higher order and appear in the
displayed spectrum.
EXTERNAL
MIXER
The EXTERNAL MIXER softkey opens a submenu for setting the parameters of the
external mixer. The softkey automatically switches on the external mixer.
EXT MIXER ON/
OFF
External mixing is switched on or off by the EXT MIXER ON/OFF softkey.
Remote command:
MIX ON
SELECT BAND The SELECT BAND softkey opens a submenu for selecting the waveguide band
and the harmonic to be used and for setting all necessary parameters. The configu-
ration can be stored using the function
SAVE of FILE menu.
Remote command:
--
When the table SELECT BAND is open and you press Enter in a BIAS field the table
is automatically closed. When the BIAS value is now changed the immediately effect
on the measurement trace can be seen.
f
in
frequency of input signal
n order of harmonic used for conversion
f
LO
frequency of 1st LO 7...13.2 GHz
f
IF
intermediate frequency 404.4 MHz
The LO frequency range cannot be used to the full due to the signal identification
functions.
(
SIGNAL ID and AUTO ID , see section “Signal Identification” on page 4.277 ).